The use of a subsoiler in combination with a main plow or turnplow is broadly known and examples of the patented prior art are contained in U.S. Pat. Nos. 1,403,618, Normandin, and 2,713,299, Shager et al. In the prior art, the constructions of the combined turnplows and subsoilders are relatively complex and costly and operating linkages are provided on the implements to move the subsoiler and/or turnplow relatively from the tractor seat or at the plow beam on which the implements are mounted.
The objective of the present invention is to simplify the construction of a combined turnplow and subsoiler and to render the movement of the subsoiler to and from active and inactive positions relative to the turnplow automatic as the combined instrument is lowered and raised as by the standard lift means of a farm tractor. In the present invention, the manual adjustment linkages of the prior art are entirely dispensed with, with the result that the implement is considerably more simplified and compact and consequently less expensive to manufacture. In the invention, when the combined implement is elevated from the ground, a counterweighted pivoted subsoiler swings automatically to an inactive retracted position with only a small drag point projecting below the bottom of the turnplow. Consequently, the complete implement may rest on the ground in a stable manner and the elevated implement will have good ground clearance during roadway transport. When the combined implement is lowered toward the ground, the drag point on the subsoiler will first penetrate the soil, and as a result of this, the pivoted subsoiler will be shifted to the active extended position relative to the turnplow automatically and without the necessity for an associated mechanical operating linkage. Retraction of the subsoiler, when the implement is elevated, is caused by gravity. The construction of the implement is extremely simple and its mode of operation is unique and efficient.
Other features and advantages of the invention will become apparent during the course of the following description.